#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <cstdio>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <unordered_set>
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using namespace atcoder;
#endif
#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define _rep(i, n) _rep2(i, 0, n)
#define _rep2(i, a, b) for(int i = (int)(a); i < (int)(b); i++)
#define rep(...) GET_MACRO(__VA_ARGS__, _rep2, _rep)(__VA_ARGS__)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
using i64 = long long;
template<class T, class U>
bool chmin(T& a, const U& b) { return (b < a) ? (a = b, true) : false; }
template<class T, class U>
bool chmax(T& a, const U& b) { return (b > a) ? (a = b, true) : false; }

template<typename T>istream& operator>>(istream&i,vector<T>&v){rep(j,v.size())i>>v[j];return i;}
template<typename T>string join(vector<T>&v){stringstream s;rep(i,v.size())s<<' '<<v[i];return s.str().substr(1);}
template<typename T>ostream& operator<<(ostream&o,vector<T>&v){if(v.size())o<<join(v);return o;}
template<typename T>string join(vector<vector<T>>&vv){string s="\n";rep(i,vv.size())s+=join(vv[i])+"\n";return s;}
template<typename T>ostream& operator<<(ostream&o,vector<vector<T>>&vv){if(vv.size())o<<join(vv);return o;}

int main(){
    int n, k;
    cin >> n >> k;
    vector<int> a(n), b(n);
    cin >> a >> b;
    vector<int> p(n);
    iota(all(p), 0);
    sort(all(p), [&](auto i, auto j){return a[i] - b[i] < a[j] - b[j];});
    string ans = "";
    rep(i, n){
        if (a[i] > b[i]){
            ans += 'A';
            k--;
        }
        else ans += 'B';
    }
    if (k < 0){
        for (int i = 0; i < n; i++){
            if (ans[p[i]] == 'A'){
                ans[p[i]] = 'B';
                k++;
                if (k == 0) break;
            }
        }
    }
    if (k > 0){
        for (int i = n - 1; i >= 0; i--){
            if (ans[p[i]] == 'B'){
                ans[p[i]] = 'A';
                k--;
                if (k == 0) break;
            }
        }
    }
    cout << ans << endl;
}